Additive processing of fluoropolymers

Abstract

Provided are methods for making shaped fluoropolymer by additive processing using fluoropolymer particles, polymerizable binder and extraction with supercritical fluids. Also provided are 3D printable compositions for making shaped fluoropolymer articles and articles comprising a shaped fluoropolymer.

The invention claimed is: 
     
       1. A method of producing a fluoropolymer article comprising:
 (i) providing a fluoropolymer article containing at least 20% by weight of a fluoropolymer based on the total weight of the article, a binder material, and an organic solvent, wherein the fluoropolymer is selected from the group consisting of fluoropolymers having a melt flow index at 372° C. and 5 kg load (MFI 372/5) of less than 1 g/10 min, wherein providing the fluoropolymer article comprises either:
 (a) subjecting a composition comprising fluoropolymer particles either dispersed in a dispersing medium comprising the organic solvent or dissolved in the organic solvent to additive processing in an additive processing device containing at least one energy source, wherein the composition comprises at least one polymerizable binder material capable of binding the fluoropolymer particles to form a layer in a part of the composition that has been exposed to the energy source of the additive processing device; 
 (b) subjecting at least a part of the composition to exposure of the energy source to form a layer by polymerizing the binder material; and 
 (c) repeating the step (b) to form a plurality of layers to create the fluoropolymer article; 
 or 
 (1) subjecting a composition comprising fluoropolymer particles dispersed in a dispersing medium comprising water or a solvent immiscible with a supercritical fluid to additive processing in an additive processing device containing at least one energy source, wherein the composition comprises at least one polymerizable binder material capable of binding the fluoropolymer particles to form a layer in a part of the composition that has been exposed to the energy source of the additive processing device; 
 (2) subjecting at least a part of the composition to exposure of the energy source to form a layer by polymerizing the binder material; 
 (3) repeating the step (2) to form a plurality of layers to create the article; and 
 (4) exchanging the water or the solvent immiscible with the supercritical fluid with the organic solvent that is miscible with the supercritical fluid to create the fluoropolymer article; and 
 
 (ii) at least partially removing the organic solvent from the article by treatment with a supercritical fluid, wherein the organic solvent is miscible with the supercritical fluid. 
 
     
     
       2. The method of  claim 1 , wherein the organic solvent is an alcohol. 
     
     
       3. The method of  claim 1 , wherein the fluoropolymer is selected from the group consisting of tetrafluoroethene homopolymers, tetrafluoroethene copolymers containing up to 1% by weight of perfluorinated alpha-olefin comonomers, and tetrafluoroethene copolymers containing more than 1% by weight and up to 30% by weight based on the weight of the polymer of perfluorinated comonomers, partially fluorinated comonomers and non-fluorinated comonomers. 
     
     
       4. The method of  claim 1 , wherein the fluoropolymer is selected from the group consisting of the fluoropolymers having a melt flow index at 372° C. and 5 kg load (MFI 372/5) of less than 0.1 g/10 min. 
     
     
       5. The method of  claim 1 , wherein the binder material comprises a material comprising polymerizable acrylate groups. 
     
     
       6. The method of  claim 1 , wherein the article contains less than 10% by weight based on the weight of the article of water. 
     
     
       7. An article made by the method of  claim 1 , the article comprising a curved surface wherein the curved surface comprises the fluoropolymer and has a surface roughness (Ra) of less than 8 μm and wherein the fluoropolymer is selected from the group consisting of tetrafluoroethene homopolymers, tetrafluoroethene copolymers containing up to 1% by weight of perfluorinated alpha-olefin comonomers, and tetrafluoroethene copolymers containing more than 1% by weight and up to 30% by weight based on the weight of the polymer of perfluorinated comonomers, partially fluorinated comonomers and non-fluorinated comonomers. 
     
     
       8. The article of  claim 7  wherein the fluoropolymer is a tetrafluoroethene copolymer containing more than 1% by weight and up to 30% by weight based on the weight of the polymer of perfluorinated comonomers, partially fluorinated comonomers and non-fluorinated comonomers and wherein the fluoropolymer has a melting point between 260° C. and 315° C. 
     
     
       9. The article of  claim 7  wherein the curved surface is a surface of a shape selected from the group consisting of cylinders, half-cylinders, spheres, half-spheres and combinations thereof. 
     
     
       10. The article of  claim 7  wherein the curved surface is an interior surface of a channel for transporting fluids or gases that is or will be exposed to the transporting fluids or gases. 
     
     
       11. The article of  claim 7  wherein the article is selected from the group consisting of molds, housings or seats of a valve, seals, pistons, joints, closure systems and a component thereof. 
     
     
       12. The article of  claim 7  being a device for processing or storing biological material comprising food, blood, tissues or pharmaceuticals.